I have in my shop one of Greg Loehr’s longboards. It is 5 years old, and made from 2LB EPS foam. It has no pressure dings or dents, however there is a little yellowing, but not much compared to poly. I know the board has been around, as I saw it in Florida, then Tucson, now here! This was the board that he used when he and Bert went surfing while Bert was in “cali”. They both commented on how both their shapers were so similar. Wonder why?
Ken
Rick, the old school boards of yesteryear, when they delam’d, the glass came off the foam, but the Clark’s as you know break down inside. I use some Walker, but haven’t seen this happen to their foam that I know of. What you say about a denser foam is right, I did a personal with classic Clark and 4oz’d it top and bottom, had I put 6 on the bottom, I would still be in great shaper after 5 years. You can add just about as much glass as you want, but if the underlying structure is weak, weak is, as weak does sir!
after having worked on my fair share of epoxy over every combination of core i can think of …
i would say the title should be more aptly titled , “urethane weirdness”…
urethane is incredibly inconsistent and anyone who works with urethane would admit , that many things can go wrong , humidity , heat or cold , operator inconsistency , all can lead to a variety of finished product quality …
also epoxy over urethane doesnt make a huge difference …
in general your laminate is thinner and lighter , so extra denting on urethane is normal , the resin and glass skin will have more range in movement before cracking , the extra range of flex in the laminate means it can dent further before it fails .
so epoxy over urethane after a while seems to have proportionatly more pressure dings …
but when taken in comparison to the same beating as p/e over p/u , the pe board will have more cracks and areas where the glass has actually broken , because the p/e has failed first …
because epoxy can bend so much further before failing , your core is now under more shear range , this shearing is breaking down the foam just below where the epoxy has penetrated the foam …
that why xps fails and delams so much easier in comparison to urethane and then eps last …
it has to do with the depth of resin penatration and then how well the foam deals with shear movement …
to date eps handles the biggest range of repeated cycles of flexing and flexes the furthest before shear failure happens …
as greg will surely agree with when he arrives back in the states …
the breaking point of each of the materials used in a composite structure need to be closely matched …
epoxy outstretches the limits of urethane foam …
there are now new core materials emerging , that have properties not yet seen in any other foam …
i just recently got a sample of a new foam that is looking for a market …
its average weight is 1.3lb , water proof and 100% memory , machinable and solvent resistent …
the fact it has such good memory properties means it may even outperform the limits of epoxy …
as one material or composite ingredient is improved it highlights the next weakest link in the structure …
right now your weak link is urethane , if your trying to finish it with a better resin …
in the past i had no vested interest appart from the boards i produced …
so my only motivation was getting the message out that epoxy is great stuff …
but now we will be doing gregs resin down here in oz , so while it may seem im backing it because were selling it …
i wouldnt put my name to crap …im behind gregs resin coz i believe in it …weve been discussing the many technical working properties of the resin , and greg has filled me in on the subtleties of the mixes , and the stuff we will be doing down here will be a slight reformulation based on production needs and will harmonise with more of a production style lineup , coming from the perspective of someone who has had epoxy in a production enviroment , some simple little things make it so much easier to get the job done …
plus on street level can answer all the technical questions new users would have …
theres some other great stuff in R&D right now …
which is being designed with standard surfboard construction in mind , shape , laminate, sand and finish …
theres some real quality alternatives starting to appear …
regards
BERT
Aloha Bert! Thanks for the informative post. I’ve been doing some major thinking about the foam failure problem. Been discussing it with a variety of informed people. I’m stoked that we came to the same conclusion as the points that you mentioned. Definitely foam failure right at the point where the resin reaches max absorbtion. It seems that epoxy is usable with urethane foam, but with some changes, ie. denser weight, more glass, etc., to create a stronger board. The amazing thing to me is that I had never realized the amount of breathability that occurs in the standard pu/pe surfboard. I attribute much of that to the adhesion of the resin to the glass fibers, and the foam. It’s no wonder that pu/pe boards are so destructable. I had never realized that until I started using RR, and noticed the almost total bond, that effectively sealed the foam, eliminating the breathing phenomenon, leading to the wierd foam failure. After seeing a few of these problem boards, I naturally freaked, and felt the need to ask some questions. This is the sort of thing that no one has mentioned previously. It all pretty much brought my pu/ epoxy program to an end. Just as well, as now I’m more free to blaze ahead into new methods and materials. All of a sudden, the old ways are obsolete! Also, I’d like to mention that I was in no way dissing Greg’s resin, or any of you pioneers in the field. I feel that it’s the best glue I’ve ever used, and don’t want to go back to using p.e.! Mahalo nui! Aloha…RH
Bert when, what, where… will gregs resin be available in west oz any idea on prices and… a light water proof foam!!! what is it??? Is it available in oz what sizes would it come in and how much?? huh I’m keen! Have been using Burfords ultra ultra light stringerless blanks(about 30kg/m3) for a couple of sailboards and sandwhiching them now I can’t get any light XPS.
Mike.
Bert and I should be in a position to provide better products for builders in the near future. As Bert stated, the foam right now is the weak point. This will, I believe, be our first concern.
As to the question Rick brought up, I posted a long explanation on the “machanical properites epoxy vs. polyester” thread.